The present invention relates generally to magnetic disk drives, and more particularly to the control of operating parameters during a write (recording) operation.
Magnetic disk drives are normally connected to a computer, server, or other electronic device, and are frequently used as large-capacity external storage devices. Performance demands are particularly high in a server environment, and a magnetic disk drive connected to a server is required to achieve data transfer at a high speed and exhibit high reliability. The demands on data write frequency and storage capacity are on the increase. To meet high performance requirements at a specified ambient temperature while offering an increased density, it is naturally demanded that the magnetic disk drive write information properly.
When the magnetic disk drive writes data or other electronic information onto a magnetic disk medium, it is essential that the distance between the magnetic head and magnetic disk medium be minimized. In reality, the magnetic head should be positioned as close as possible to the magnetic disk medium by minimizing the floating height of the magnetic slider on which the magnetic head is mounted.
A technology disclosed by Japanese Patent Laid-open No. 5-20635 forms a resistive element in the magnetic head or magnetic slider and energizes the resistive element to cause the magnetic head element to protrude, thereby reducing the gap between the magnetic pole end and magnetic disk surface.
When the above conventional technology is taken into consideration, there is no alternative but to determine the spacing between the write head element and magnetic disk medium surface by predicting the thermal expansion and protrusion (thermal protrusion) of the magnetic head. Consequently, at an early stage of a write operation prior to magnetic head thermal expansion and protrusion, the spacing between the write head element and magnetic disk medium has to be several nanometers greater than after a predefined degree of thermal expansion is achieved. It means that the writing capacity may be inadequate at an early stage of a write operation. The writing capacity is insufficient especially when the magnetoresistivity (hereinafter abbreviated to Hc) of the magnetic disk medium is great.
A technology disclosed by Japanese Patent Laid-open No. 10-334402 provides a technology for causing an adequately large write current to flow to the write head so as to perform a write at a low temperature. Further, a technology disclosed by Japanese Patent Laid-open No. 2002-237004 controls the write current in accordance with the ambient temperature by changing the write current when a certain threshold temperature is exceeded.